It has previously been proposed to adjust the engagement pressure of two printing cylinders by sensing the engagement pressure between the bearer rings by mechanical measuring means. For example, the engagement pressure of the working cylinders of a rotary printing machine can be measured by sensing the gap between adjacent bearer rings, which causes elastic deformation thereof, by placing special measuring rollers in the gap between the bearer rings. The flattening of the bearer rings, due to elastic deformation, is in the order of from between about 0.1 to 0.3 mm (see, for example, German Published Patent Application DE-AS No. 23 00 946). Mechanically measuring the deformation has the disadvantage that manufacturing tolerances of the mechanical measuring elements, as well as out-of-round deviations of the bearer rings, for example due to wear thereof, can falsify the measuring results.